Controlled non-normal alignment of catalytically grown nanostructures in a large-scale synthesis process

ABSTRACT

Systems and methods are described for controlled non-normal alignment of catalyticaly grown nanostructures in a large-scale synthesis process. A method includes: generating an electric field proximate an edge of a protruding section of an electrode, the electric field defining a vector; and forming an elongated nanostructure located at a position on a surface of a substrate, the position on the surface of the substrate proximate the edge of the protruding section of the electrode, at least one tangent to the elongated nanostructure i) substantially parallel to the vector defined by the electric field and ii) substantially non-parallel to a normal defined by the surface of the substrate.

This invention was made with United States Government support undercontract to UT-Battelle, L.L.C. The Government has certain rights inthis invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of nanotechnology. Moreparticularly, the invention relates to nanostructures that areelongated, methods of making elongated nanostructures and machinery formaking such nanostructures.

2. Discussion of the Related Art

The fabrication of commercially valuable devices based upon nanoscalecomponents requires large-scale processes that allow massive productionof these components. As a practical matter, such large scale processesneed to i) mass produce nanoscale components with well specifiedproperties, (e.g., shape, structure, chemical composition, etc.), ii)enable secure placement of these components in an appropriateorientation that may be dictated by end product functionality, and iii)facilitate attachment of robust input and output (IO) connections.

Elongated nanostructures are exemplified by carbon nanofibers and carbonnanotubes. Carbon nanotubes are a material with superior electronic andmechanical properties. Several research groups have recentlydemonstrated fabrication of nanoscale devices based upon carbonnanotubes (Collins and Arnold, 2001; Rueckes et al., 2000; Choi et al.,1999; Stevens et al., 2000). Despite vast advances in this field, thereremain unsolved problems such as the requirements to (a) synthesizelarge quantities of CNTs with predetermined properties, (b) place themin a required configuration and (c) create IO connections, all in thecontext of a fast mass production fabrication process.

The suitability of vertically aligned carbon nanofibers (VACNFs) andvertically aligned carbon nanotubes (VACNTs) for nanoscale devicefabrication has been previously demonstrated (Guillom et al., 2001).VACNFs have been deterministically synthesized at predeterminedlocations using large-scale fabrication processes such as lithographyand plasma-enhanced chemical vapor deposition (PECVD). The deterministicVACNF growth that has been achieved includes the control of thelocation, length, diameter, and shape of VACNFs (Merkulov et al., 2001;Merkulov et al., 2000). The control of the VACNF orientation hasgenerally been limited to the direction perpendicular (normal) to thesubstrate. What is needed is a mass production technology that can (i)fabricate large quantities of elongated nanostructures withpredetermined properties, (ii) place them in a required configurationand (iii) facilitate the creation of IO connections.

Heretofore, the requirements of synthesizing large quantities ofelongated nanostructures with well defined properties, arranging them ina desired configuration, and facilitating the creation of input/outputconnections have not been fully met. What is needed is a solution thatsimultaneously addresses all of these requirements.

SUMMARY OF THE INVENTION

There is a need for the following embodiments. Of course, the inventionis not limited to these embodiments.

According to an aspect of the invention, a method comprises: generatingan electric field proximate an edge of a protruding section of anelectrode, the electric field defining a vector; and forming anelongated nanostructure located at a position on a surface of asubstrate, the position on the surface of the substrate proximate theedge of the protruding section of the electrode, at least one tangent tothe elongated nanostructure i) substantially parallel to the vectordefined by the electric field and ii) substantially non-parallel to anormal defined by the surface of the substrate. According to anotheraspect of the invention, a method comprises: generating an electricfield proximate a position on a surface of a substrate, the electricfield defining a vector; forming an elongated nanostructure located atthe position on the surface of the substrate; then changing a directionassociated with the vector; and continuing to form the elongatednanostructure, at least one tangent to the elongated nanostructuresubstantially non-parallel to a normal defined by the surface of thesubstrate. According to another aspect of the invention, a methodcomprises: generating an electric field proximate a position on asurface of a substrate, the electric field defining a vector; forming anelongated nanostructure located at the position on the surface of thesubstrate; then moving the position on the surface of the substrate; andcontinuing to form the elongated nanostructure, at least one tangent tothe elongated nanostructure substantially nonparallel to a normaldefined by the surface of the substrate. According to another aspect ofthe invention, a composition comprises an elongated nanostructureincluding a first segment defining a first axis and a second segmentcoupled to the first segment, the second segment defining a second axisthat is substantially nonparallel to the first axis. According toanother aspect of the invention, an apparatus comprises an electrodeincluding: a protruding section defining an edge; and a nonprotrudingsection coupled to the protruding section, wherein the edge is adaptedto deflect an electric field generated with the electrode and at leastone section selected from the group consisting of the protruding sectionand the nonprotruding section is adapted to support a substrate for thegrowth of elongated nanostructures.

These, and other, embodiments of the invention will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingvarious embodiments of the invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manysubstitutions, modifications, additions and/or rearrangements may bemade within the scope of the invention without departing from the spiritthereof, and the invention includes all such substitutions,modifications, additions and/or rearrangements.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings accompanying and forming part of this specification areincluded to depict certain aspects of the invention. A clearerconception of the invention, and of the components and operation ofsystems provided with the invention, will become more readily apparentby referring to the exemplary, and therefore nonlimiting, embodimentsillustrated in the drawings, wherein like reference numerals (if theyoccur in more than one view) designate the same elements. The inventionmay be better understood by reference to one or more of these drawingsin combination with the description presented herein. It should be notedthat the features illustrated in the drawings are not necessarily drawnto scale.

FIGS. 1A and 1B illustrate schematic views of angled and kinkednanostructures, representing embodiments of the invention.

FIGS. 2A and 2B illustrate schematic views of cathode-anodeconfigurations, representing embodiments of the invention.

FIGS. 3A–3C illustrate views of nanostructures coupled to a cathode,representing embodiments of the invention.

FIGS. 4A–4E illustrate views of angled nanostructures coupled to acathode, representing embodiments of the invention.

FIG. 5 illustrates a plot of carbon nanofiber orientation to normalversus distance from a cathode edge, representing embodiments of theinvention.

FIGS. 6A–6F illustrate views of nanostructures, representing embodimentsof the invention.

FIGS. 7A–7C illustrate views of kinked nanostructures, representingembodiments of the invention.

FIGS. 8A–8B illustrate schematic views of a plural cathode-anodeconfiguration, representing an embodiment of the invention.

FIGS. 9A–9B illustrate schematic views of a plural cathode-anodeconfiguration that is reconfigurable, representing an embodiment of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention and the various features and advantageous details thereofare explained more fully with reference to the nonlimiting embodimentsthat are illustrated in the accompanying drawings and detailed in thefollowing description. Descriptions of well known starting materials,processing techniques, components and equipment are omitted so as not tounnecessarily obscure the invention in detail. It should be understood,however, that the detailed description and the specific examples, whileindicating preferred embodiments of the invention, are given by way ofillustration only and not by way of limitation. Various substitutions,modifications, additions and/or rearrangements within the spirit and/orscope of the underlying inventive concept will become apparent to thoseskilled in the art from this disclosure.

Within this application several publications are referenced by author'sname and publication year within parentheses. Full citations for these,and other, publications may be found at the end of the specificationimmediately preceding the claims after the section heading References.The disclosures of all these publications in their entireties are herebyexpressly incorporated by reference herein for the purpose of indicatingthe background of the invention and illustrating the state of the art.

The below-referenced U.S. Patent Applications disclose embodiments thatwere satisfactory for the purposes for which they are intended. Theentire contents of U.S. patent application Ser. No. 09/795,660, filedFeb. 27, 2001, and U.S. patent application Ser. No. 09/810,531, filedMar. 15, 2001, are hereby expressly incorporated by reference herein forall purposes.

In general, the context of the invention is nanotechnology. The contextof the invention can include physics, such as for example scanning probemicroscopy. The context of the invention can also include chemistry,such as for example, molecular synthesis.

The invention can include one or more elongated nanostructures having aprincipal axis that is aligned at a non-normal angle relative to asupporting substrate. The invention can also include one or moreelongated nanostructures whose principal axis is deviated. The inventionthus relates to elongated nanostructures of the type that can be termedkinked.

The invention can include methods of making the non-normal alignedand/or deviated elongated nanostructures. The invention can also includeapparatus for making the nonnormal aligned and/or deviated elongatednanostructures.

FIGS. 1A and 1B depict a schematic representation of the tip shapesrequired for inspecting (FIG. 1A) wide and (FIG. 1B) narrow trenches. InFIG. 1A, a cantilever 110 is coupled to an elongated nanostructure 120.The elongated nanostructure 120 is shown contacting a sidewall of a widetrench 130. In FIG. 1B, another cantilever 140 is coupled to a kinkedelongated nanostructure 150. The kinked elongated nanostructure 150 isshown contacting a sidewall of a narrow trench 160. The angulardeviation of the kinked elongated nanostructure 150 permits thestructure to penetrate the narrow trench 160 at a steep angle, therebyenabling sensing of deeply receded features. The kinked elongatednanostructure 150 in FIG. 1B is also suitable for inspecting widetrenches.

The ability to control the orientation of a nanoscale object over abroad range of angles is a very important technological and scientificaspect and can be highly beneficial for production of various nanoscaledevices. For instance, fabrication of probes for scanning microscopy inwhich a cantilever tip is oriented at a relatively large angle to thenormal to the cantilever surface could allow inspection of sidewalls ofrelatively wide trenches (see FIG. 1A), and a kinked tip would allowinspection of narrow trenches (FIG. 1B). The ability to do suchinspection can be quite valuable for many applications in varioustechnological fields, in particular for the semiconductor industry. Theinvention can include a method for synthesis of aligned CNFs, in whichthe CNF orientation is not fixed to the direction parallel to thesubstrate normal but can be controlled over a wide range of angles. Thealignment control aspect of the invention is not limited to CNFs or CNTsonly but can be applied for any other structures whose growth process issimilar to the catalytic growth of CNFs/CNTs (Merkulov et al., 2001;Baker, 1989). The invention can also include an apparatus that allowsmass production of variably oriented CNFs.

The invention can include a method for controlling the alignment ofcatalytically grown nanostructures, in particular carbon nanotubes(CNTs) and/or nanofibers (CNFs), in a plasma-enhanced chemical vapordeposition process. The control of alignment can be achieved bypositioning the samples in the vicinity of geometrical features of thesample holder, where bending of the electric field lines occurs. Thegrowth of CNFs aligned at various angles to the substrate and kinkedCNFs that include two parts aligned at different angles has beendemonstrated. In addition, the invention can include a design of anapparatus that allows mass-production of nanostructures aligned at avariable angle to the substrate and of kinked nanostructures with angledtips.

In order to initiate growth of a single CNT or CNF, formation ofcatalyst nanoparticles may be required (Merkulov et al., 2000). Nickel(Ni) and nickel-iron (Ni—Fe) alloy catalysts can be used. However, othercatalysts, such as Fe, Co, etc. can be utilized as well. To form“forests” of chaotically placed CNFs, catalyst thin films were used. Forsynthesis of individual CNFs, catalyst dots were produced using electronbeam lithography and metal evaporation. The catalyst nanoparticles wereformed by dc plasma pre-etching of the catalyst thin films with ammoniaand annealing them at the elevated temperatures (˜700° C.) in a vacuumchamber. Direct-current (dc) plasma-enhanced chemical vapor deposition(PECVD) was used to produce vertically aligned carbon nanostructures.However, other plasma deposition techniques such as RF (radio frequency)or microwave plasma CVD can also be used. A mixture of a carbonaceousgas (e.g., acetylene) and an etchant (e.g., ammonia) was used. Thesubstrates were heated directly by placing them on a heater plate (thecathode of the plasma discharge) and the growth temperature was ˜700°C., although higher and lower temperatures can be used.

FIGS. 2A and 2B depict a schematic representation of the cathode-anodeconfiguration and the corresponding electric field lines (dotted line)that form in the absence (FIG. 2A) and presence (FIG. 2B) of the plasma.In FIG. 2A an anode 210 is coupled to a cathode 220 that includes aprotuberance 230. The protuberance can be termed a sample holder, asubstrate or simply one of the electrodes, in this example, the cathode.Further, separate sample holder(s) and/or separate substrate(s) can becoupled to the protuberance. The resulting field lines are demarcated bydashed lines. The electrode and cathode are generically known aselectrodes and conventionally demarcated by an applied basis. Theinvention is not limited to locating the protuberance 230 on the cathode220 since the invention can include locating the protuberance on theanode.

In FIG. 2B, a plasma 240 has been introduced. Again, the field lines aredemarcated by dashed lines. It can be appreciated that the presence ofthe plasma changes the shape and/or density of the field lines. Thischange can be termed deflection and the resulting field lines deflected.It is important to appreciate that, although the field line around theentire sidewall of the protuberance are affected, the field linesnearest the edges defined by the protuberance 230 are affected most bythe introduction of the plasma 240.

Without being bound by theory, the orientation of CNFs synthesized byPECVD may occur due to the presence of the catalytic nanoparticle at theCNF tip and/or an electric field that is present during the growthprocess. In the past the field has nominally been directed perpendicularto the substrate surface (Merkulov et al., 2001). In contrast, theinvention can include the use of a field that is substantiallynonperpendicular to the substrate surface. Without being bound bytheory, the direction of the electric field lines may determine theorientation of the elongated nanostructures (e.g., CNFs). Therefore, inorder to control the CNF orientation, the direction of the electricfield lines may need to be controlled. One way to achieve this controlis to control the angle between an anode surface and a cathode surface,given that no physical shielding of the electric field (e.g., plasma) ispresent between the two electrodes. An example of such an arrangement isshown in FIG. 2A. While the anode is a flat plate, the cathode can have,for example, a three dimensionally extended rectangular shape. As aresult, around the top facet of the cathode the electric lines arenormal to the surface, whereas around the cathode sidewalls, bending ofthe electric field lines occurs. Thus, synthesis of CNFs oriented atsome angle to the normal is possible. The inventors note that for thefield line bending to occur, the cathode does not need to have arectangular shape, but can have a triangular, trapezoidal, circular,oval, or any other cross section, extended shape. The inventors alsonote that in the absence of plasma the relative positions and/orfunctions of the anode and cathode can be reversed. The important pointis that the cathode (anode) face at which the catalyst nanoparticleand/or growing top of the structure is located should be oriented at anon-zero angle relative to the anode (cathode) plane.

In contrast to the situation described with reference to FIG. 2A above,during a PECVD process a plasma is present between the two electrodes,as shown in FIG. 2B, the plasma surrounds all faces of the sample holder(nominally in this description the cathode). Consequently, the entiresample holder surface, except for the regions around the edges, issurrounded by electric field lines that are straight and orientedperpendicular to the surface of the cathode. As a result, CNFs locatedfar enough from the edges are aligned perpendicular to the substratesurface, regardless of whether the growth occurs on the top face or thesidewalls of the sample holder (i.e., in this description, the cathode).This is illustrated in FIGS. 3A–3C which show two CNF forests grown onthe top and sidewall faces (coupled substrates) of the sample holder.

Referring to FIG. 3A, a first substrate 340 has been located on aprotuberance 330 that composes a cathode 320. The first substrate 340can be removably connected to the protuberance 330. A plurality ofelongated nanostructures 350 are coupled to the first substrate 340. Theplurality of elongated nanostructures 350 are substantially parallel toa normal to the first substrate 340 since the field lines above thefirst substrate 340 are substantially parallel to the normal to thefirst substrate. A second substrate 360 has also been located on theprotuberance 330. The second substrate 360 can also be removablyconnected to the protuberance 330. Another plurality of elongatednanostructures 370 are coupled to the second substrate 360. The anotherplurality of elongated nanostructures 370 are substantially parallel toa normal to the second substrate 360 since the field lines at the secondsubstrate 360 are substantially parallel to the normal to the firstsubstrate. Since the plane of the second substrate is perpendicular tothe plane of the first substrate, the second plurality of elongatednanostructures are perpendicularly orientated with regard to the firstplurality of elongated nanostructures.

Together, FIGS. 3A–3C depict a schematic representation of an actualexperimental setup during a PECVD process, in which the substrates arelocated far from the sample holder (nominally the cathode) edges. FIGS.3B–3C are scanning electron microscopy images showing that the resultantCNFs are substantially vertically aligned, regardless of whether thesubstrate was placed on top or sidewalls of the sample holder. As willbe discussed in more detail below, had the substrates be positionedcloser to the edges, the resultant CNFs would not have beensubstantially vertically aligned. Referring to FIG. 4A, an electrode 420includes a sample holder 430. A substrate 440 is removably coupled to asurface 435 of the sample holder 430. A plurality of elongatednanostructures 450 are coupled to the substrate 440. The sample holderdefines a sample holder edge 445 which is proximate a substrate edge 455of the substrate 440.

Together, FIGS. 4A–4E depict schematic representation of an actualexperimental setup during the PECVD process, in which the substrate islocated close to the sample holder edge, (FIG. 4A) and scanning electronmicroscopy images showing the resultant CNF forests located at (FIG. 4B)100, (FIG. 4C) 500, (FIG. 4D) 1000, and (FIG. 4E) 2000 μm away from theedge and aligned at ˜38, 26, 12, and 5° angles to the substrate normal,respectively.

Far away from the cathode edges the electric field lines are straightand perpendicular to the normal to the cathode surface. However, thedirection and shape of the field lines is different around the cathodeedges. Significant bending of the electric field lines occurs in thatregion around the edges. The closer to the edge the nanostructures aregrown, the more bending takes place. At the very edge the bending is thelargest. As the distance away from the edge increases, the field linebending decreases until the lines become perfectly straight. Thus, it ispossible to employ this phenomenon to synthesize CNFs that are alignedat a variable angle to the substrate normal. FIG. 4A shows anexperimental set up in which the substrate edge is aligned with that ofa sample holder having a rectangular-like shape. In this case, the CNFalignment will deviate the most from the normal to the substrate at thesubstrate/sample holder edge. As the distance from the edge increases,the alignment becomes closer to the normal until perfectly vertical(perpendicular to the substrate) CNFs (VACNFs) are obtained. As shown inFIG. 4B-E CNFs with variable alignment angle can be synthesized this wayand the alignment angle depends on the distance between the CNF locationand the substrate/sample holder edge.

The invention can include starting the elongated nanostructure growthprocess with the substrate in a first position relative to aprotuberance edge and/or field line orientation, and then moving thesubstrate. The growth process can be interrupted during movement of thesubstrate to create an abrupt change in the shape of the structure,and/or the growth process can be continuous, thereby creating a curvedshape. Movement of the substrate can be achieved inside the PECVD vacuumchamber with actuators that are readily commercially available.

FIG. 5 depicts a plot showing the CNF alignment angle to the substratenormal as a function of the distance away from the sample holder edge.The deterministic alignment angle of the VACNF forest as a function ofthe distance from the edge is shown in FIG. 5. It can be clearly seenthat the angle relative to the normal decreases with the distance awayfrom the edge and approaches zero at large distances. The meaning oflarge being in-part a function of the field strength.

FIGS. 6A–6F depict SEM images, taken at (FIG. 6A) 0 and (FIG. 6B) 45°tilt angles, of an array of individual CNFs grown in the vicinity (˜10μm) of the substrate and the sample holder edge and of single CNFs grownat ˜(FIG. 6C) 10, (FIG. 6D) 80, (FIG. 6E) 300, and (FIG. 6F) 580 μm fromthe edge and aligned at ˜42, 30, 15, and 6° to the substrate normal. Theimages in (FIGS. 6C–6F) were taken at a 45° tilt angle.

Still referring to FIGS. 6A–6F, the invention makes possible thesynthesis of individual CNFs aligned at a variable angle to thesubstrate normal. To grow individual CNFs, patterned catalyst dots of˜100 nm in diameter were formed. Following this, the sample waspositioned on the cathode sample holder so that the catalyst dots werelocated close to the edge, similar to the arrangement in FIG. 4A. Theresultant CNFs, located close to the edge of the substrate/sampleholder, are aligned at a relatively large angle to the normal, as shownin FIGS. 6A and 6B. Just as in the case of the CNF forests, thealignment angle of individual CNFs also is a function of the distancefrom the substrate/sample holder edge. This variation can be appreciatedfrom FIG. 6C-F.

FIGS. 7A–7C depict SEM images of (FIG. 7A) a forest of and (FIGS. 7B–7C)individual kinked CNFs (KCNFs). KCNFs can include two sections: thevertical base and the tip oriented at a non-zero angle to the substratenormal. KCNFs are grown in a two step process: (I) catalyst located farfrom the sample holder edge (vertical growth direction) and catalystlocated close to the sample holder edge (off vertical growth direction).

KCNFs are just one example of a generic class of kinked elongatednanostructures. The kinking process can be applied to carbon nanotubes,as well as to fibers and tubes of other materials. Geometrically, kinked(kinky) elongated nanostructures may be defined as including a firstsegment defining a first axis and a second segment coupled to the firstsegment, the second segment defining a second axis that is substantiallynonparallel to the first axis.

The ability to control the CNF alignment allows for synthesis of kinkedstructures such as that shown in FIG. 1B. Such a kinked structureincludes two sections: a section that is aligned substantiallyperpendicular to the substrate and a second section that is aligned at asubstantially non-zero angle to the substrate normal. The first sectioncan be synthesized when the catalyst pattern, at which the CNF growthoccurs, is located at a large distance from the sample holder edge. Inthis case, the electric field lines are straight and perpendicular tothe substrate surface and vertically aligned CNFs are formed. Followingthis, the substrate can be repositioned such that the catalyst islocated near the sample holder edge. In this repositioned case, bendingof the electric field lines occurs at the CNF location and CNFs start togrow off normal. As a result, kinked CNFs (KCNF) such as shown in FIG. 7can be formed.

Of course, the kinked structure can include more than two sections.Third, fourth or more sections can be located before, between, or afterthe first and second sections.

FIGS. 8A–8B depict side (FIG. 8A) and top (FIG. 8B) views of a sampleholder arrangement that allows large-scale fabrication of devices basedon elongated nanostructures (e.g., CNFs) that are oriented at a non-zerodegree to the substrate normal. The substrate holder provides multiplesteps at which the electric field line bending occurs and consequentlyvariably aligned CNFs can be produced. At the upper corners of thesample holder, CNFs with alignment pointed outward from the center ofthe substrate can be produced. In contrast, the lower corners of thesample holder can yield CNFs that are aligned toward the center of thesubstrate.

Referring to FIG. 8A, an elevational view of a plurality ofprotuberances 810 coupled to an electrode 820 is depicted. In thisembodiment, two upper pluralities of substrates 830 and two lowerpluralities of substrates 840 is associated with each of theprotuberances 810. A plasma represented by dots is located between theelectrode 820 and another electrode 850. It can be appreciated that thefield lines cause the elongated nanostructures being grown on the upperpluralities of substrates to tilt away from the centers of thesubstrates, while the elongated nanostructures being grown on the lowerpluralities of substrates tilt in toward the center of the substrates.Thus, the “sign” (inward, outward) of the CNF angle to the normal can bechanged by controlling the placement of the substrate on the upper orlower (or intermediate) surfaces of the sample holder. Although in thisembodiment all of the protuberances 810 are coupled to a singleelectrode in a planar arrangement, the protuberances could be coupled toa multiplicity of electrodes and/or arranged in a nonplanar array.

Referring to FIG. 8B, a top view of the apparatus shown in FIG. 8A isdepicted. From this view it can be seen that each of the elongatednanostructures is coupled to its own substrate. The substrates canfunction as input and/or output connections. Thus, the elongatednanostructures can be individually robustly coupled to an I/Oconnection.

The optimal growth conditions can be different for the upper and lowersurfaces. Thus, separate growth runs may be required for the inward andoutward aligned CNFs. The alignment angle can be controlled by changingthe distance between the CNF location and the sample holder edge: thesmaller the distance, the larger the angle. As can be clearly seen fromFIGS. 8A and 8B, large-scale deposition, i.e. synthesis of multiplesamples in a single growth run, is possible.

FIGS. 9A–9B depict a schematic representation of a sample holder thatallows synthesis of kinked CNFs (KCNFs) without interrupting the growthprocess. In the “IN” position the movable part of the sample holdercreates a flat surface in the sample plane and therefore vertical CNFsare obtained (FIG. 9A). In the “OUT” position, the movable part is movedaway so that multiple steps are formed on the sample holder. As aresult, bending of the field lines occurs, the CNF growth starts toproceed in an off-vertical direction, and KCNFs are obtained.

Referring to FIG. 9A, an electrode 910 includes a first section 920 anda second section 930. The first section 920 includes three subsections921, 922, 923. Two pluralities of substrates 950 are shown on each ofthe subsections 921, 922 and 923. An elongated nanostructure is coupledto each of the substrates 950. The second section 930 is movable and isshown in FIG. 9A in an exposed (in) position. The second section 930 canalso include subparts that are optionally independently movable. Aplasma represented by dots can be generated between the electrode 910and a counter electrode 940. In this configuration, the field lines aresubstantially perpendicular to the plane of the substrates. Therefore,the elongated nanostructure segments 961 grown with the apparatus inthis configuration are substantially parallel to the normals to thesubstrates 950. Referring to FIG. 9B, the second section 930 is shown ina retracted (out) position. In this way, the first section takes on thequality of a protruding section. Alternatively, the second section 930can be lowered into the body of the electrode 910. In anotheralternative embodiment, the first section can be raised up from the bodyof the electrode 910. The first section 920 can be termed a protrudingsection since it has the capability of extending beyond the secondsection 930. The second section 930 can be termed a nonprotrudingsection since it has the capability of being both flush and recessed. Inthe configuration shown in FIG. 9B, the field line are deflected nearthe edges 950 defined by the first section 920. The elongatednanostructure segments 962 grown with the apparatus in thisconfiguration are substantially nonparallel to the normals to thesubstrates 950. The degree of deviation can be controlled by adjustingthe relative positions between the first section 920 and the secondsection 930 and by adjusting the distance between the substrates 950 andthe edge of the first section 920.

As noted above, FIGS. 9A and 9B show a possible configuration of asample holder that allows synthesis of KCNFs without interrupting thegrowth process. The sample holder includes two parts that can moverelative to each other. During the growth of the vertical part of KCNFs,the movable part of the sample holder is moved in (up in FIG. 9 a) sothat the edges of the two parts coincide (FIG. 9A). This creates avirtually flat continues surface in the substrate plane and consequentlyvertically aligned CNFs are formed. Following this, the movable part ofthe substrate holder is moved out (down in FIG. 9B) so that the stepsaround the substrate edges are created (FIG. 9B). The electric fieldlines will bend at the step edges that are revealed by moving themovable part out and consequently KCNFs similar to those shown in FIG. 7will be formed.

The disclosed embodiments show the upper and lower end edges of a threedimensional rectangle as the structure for performing the function ofdeflecting the electric field from an orientation normal to thesubstrate, but the structure for deflecting the electric field can beany other structure capable of performing the function of deflecting thefield, including, by way of example, a circle, an oval or ellipse, acube, or pyramid, or any other shape.

While not being limited to any particular performance indicator ordiagnostic identifier, preferred embodiments of the invention can beidentified one at a time by testing for the presence of non-normalaligned elongated nanostructures. The test for the presence of alignednanostructures can be carried out without undue experimentation. Theterms a or an, as used herein, are defined as one or more than one. Theterm plurality, as used herein, is defined as two or more than two. Theterm another, as used herein, is defined as at least a second or more.The terms including and/or having, as used herein, are defined ascomprising (i.e., open language). The term coupled, as used herein, isdefined as connected, although not necessarily directly, and notnecessarily mechanically. The term approximately, as used herein, isdefined as at least close to a given value (e.g., preferably within 10%of, more preferably within 1% of, and most preferably within 0.1% of).The term substantially, as used herein, is defined as largely but notnecessarily wholly that which is specified. The term generally, as usedherein, is defined as at least approaching a given state (e.g.,preferably within 10% of, more preferably within 1% of, and mostpreferably within 0.1% of). The term deploying, as used herein, isdefined as designing, building, shipping, installing and/or operating.The term means, as used herein, is defined as hardware, firmware and/orsoftware for achieving a result. The term program or phrase computerprogram, as used herein, is defined as a sequence of instructionsdesigned for execution on a computer system. A program, or computerprogram, may include a subroutine, a function, a procedure, an objectmethod, an object implementation, an executable application, an applet,a servlet, a source code, an object code, a shared library/dynamic loadlibrary and/or other sequence of instructions designed for execution ona computer system.

Practical Applications of the Invention

A practical application of the invention that has value within thetechnological arts is atomic force microscopy (AFM), scanning tunnelingmicroscopy (STM), and other scanning probe microcopies. The invention isuseful in conjunction with nanoelectronics. The invention is useful inconjunction with biological probes. Further, the invention is useful inconjunction with any other techniques where nanostructures aligned at avariable angle to the substrate can be utilized. There are virtuallyinnumerable uses for the invention, all of which need not be detailedhere.

Advantages of the Invention

The invention, can be cost effective and advantageous for at least thefollowing reasons. The invention allows the fabrication ofnanostructures aligned at a (continuously) variable angle to thesubstrate, not just vertically aligned nanostructures. The inventionallows the fabrication of “kinked” nanostructures that consist ofseveral sections that all can be aligned at different angles to thesubstrate. The invention improves quality and/or reduces costs comparedto previous approaches.

All the disclosed embodiments of the invention disclosed herein can bemade and used without undue experimentation in light of the disclosure.The invention is not limited by theoretical statements recited herein.Although the best mode of carrying out the invention contemplated by theinventor(s) is disclosed, practice of the invention is not limitedthereto. Accordingly, it will be appreciated by those skilled in the artthat the invention may be practiced otherwise than as specificallydescribed herein.

Fabrication of nanostructures other than CNFs or CNTs. The onlyrequirement is that the growth process of these nanostructures should besimilar to the catalytic growth of CNFs/CNTs. Different sample holdershape can be used. Different catalyst can be used. Different gasses canbe used.

Further, the individual components need not be formed in the disclosedshapes, or combined in the disclosed configurations, but could beprovided in virtually any shapes, and/or combined in virtually anyconfiguration. Further, the individual components need not be fabricatedfrom the disclosed materials, but could be fabricated from virtually anysuitable materials. Further, variation may be made in the steps or inthe sequence of steps composing methods described herein. Further,although the electrode described herein can be a separate module, itwill be manifest that the electrode may be integrated into the systemwith which it is associated. Furthermore, all the disclosed elements andfeatures of each disclosed embodiment can be combined with, orsubstituted for, the disclosed elements and features of every otherdisclosed embodiment except where such elements or features are mutuallyexclusive.

It will be manifest that various substitutions, modifications, additionsand/or rearrangements of the features of the invention may be madewithout deviating from the spirit and/or scope of the underlyinginventive concept. It is deemed that the spirit and/or scope of theunderlying inventive concept as defined by the appended claims and theirequivalents cover all such substitutions, modifications, additionsand/or rearrangements.

The appended claims are not to be interpreted as includingmeans-plus-function limitations, unless such a limitation is explicitlyrecited in a given claim using the phrase(s) “means for” and/or “stepfor.” Subgeneric embodiments of the invention are delineated by theappended independent claims and their equivalents. Specific embodimentsof the invention are differentiated by the appended dependent claims andtheir equivalents.

REFERENCES

-   Collins, Arnold, Avouris, Science, 292:706, 2001.-   Rueckes, Kim, Joselevich, Tseng, Cheung, Lieber, Science, 289:94,    2000.-   Choi, Chung, Kang, Kim, Jin, Han, Lee, Jung, Lee, Park, Kim, Appl.    Phys. Lett., 75:3129, 1999.-   Stevens, Nguyen, Cassell, Delzeit, Meyyappan, Han, Appl. Phys.    Lett., 77:3453, 2000.-   Guillorn, Simpson, Bordonaro, Merkulov, Baylor, Lowndes, Vac. Sci.    Techol., B19:573, 2001.-   Merkulov, Guillorn, Lowndes, Simpson, Voelkl, Appl. Phys. Lett.,    79:1178, 2001.-   Merkulov, Lowndes, Wei, Eres, Voelkl, Appl. Phys. Lett., 76:3555,    2000.-   Chen, Shaw, Guo, Appl. Phys. Lett., 76:2469, 2000.-   Baker, Carbon, 27:315, 1989.-   Merkulov, Melechko, Guillorn, Lowndes, Simpson, Appl. Phys. Lett.,    79:2970, 2001.-   Ren, Huang, Wang, Wen, Xu, Wang, Calvet, Chen, Klemic, Reed, Appl.    Phys. Lett., 75:1086, 1999.

1. A method, comprising: generating an electric field proximate an edgeof a protruding section of an electrode, the electric field defining avector; and forming an elongated nanostructure located at a position ona surface of a substrate, the position on the surface of the substrateproximate the edge of the protruding section of the electrode, at leastone tangent to the elongated nanostructure i) substantially parallel tothe vector defined by the electric field and ii) substantiallynon-parallel to a normal defined by the surface of the substrate.
 2. Themethod of claim 1, wherein forming includes plasma enhanced chemicalvapor deposition.
 3. The method of claim 1, wherein forming theelongated nanostructure includes forming a plurality of substantiallyaligned nanostructures.
 4. The method of claim 3, wherein the pluralityof substantially aligned nanostructures include a plurality of carbonnanofibers.
 5. The method of claim 3, wherein the plurality ofsubstantially aligned nanostructures include a plurality of carbonnanotubes.
 6. The method of claim 3, wherein the plurality ofsubstantially aligned nanostructures are formed using a plurality ofcatalyst nanoparticles including at least one element selected from thegroup consisting of nickel, iron and cobalt.
 7. The method of claim 1,further comprising: changing a direction associated with the vector; andcontinuing to form the elongated nanostructure.
 8. The method of claim7, wherein changing the direction associated with the vector includesmoving the protruding part of the electrode relative to a nonprotrudingpart of the electrode.
 9. The method of claim 1, further comprisingmoving the substrate relative to the edge of the protruding section ofthe electrode.
 10. A product made by the method of claim 1.